Semiconductor light-emitting device

ABSTRACT

A semiconductor light-emitting device includes a lead frame, a semiconductor light-emitting element mounted on the top surface of the bonding region, and a case covering part of the lead frame. The bottom surface of the bonding region is exposed to the outside of the case. The lead frame includes a thin extension extending from the bonding region and having a top surface which is flush with the top surface of the bonding region. The thin extension has a bottom surface which is offset from the bottom surface of the bonding region toward the top surface of the bonding region.

This application is a Continuation of application Ser. No. 13/414,294,filed Mar. 7, 2012, which is a Continuation of application Ser. No.12/890,964, filed Sep. 27, 2010, which is a Division of application Ser.No. 12/079,760, filed Mar. 28, 2008, which applications are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor light-emitting deviceprovided with a semiconductor light-emitting element.

2. Description of the Related Art

FIGS. 6 and 7 illustrate an example of conventional semiconductorlight-emitting device (see JP-A-2005-353914, for example). Theillustrated semiconductor light-emitting device X includes a lead frame91, an LED chip 92, a case 93, and a transparent resin 94. The leadframe 91 includes two strip portions, i.e., a relatively long portion 91a and a relatively short portion 91 b, as seen from FIG. 6. These twoportions, having the same width as seen from FIG. 7, are fitted into alower space in the case 93 in a manner such that the bottom surface ofthe lead frame 91 is exposed out of the case 93. The LED chip 92 servesas a light source of the semiconductor light-emitting device X, and isbonded to the longer strip portion 91 a of the lead frame 91. The LEDchip 92 is connected to the shorter strip portion 91 b of the lead frame91 via a wire 95. The light-emitting device X may be mounted on aprinted circuit board, for example.

In order to obtain stronger light emission from the semiconductorlight-emitting device X, it is required to apply greater electricalpower to the LED chip 92. Inevitably, the amount of heat generated bythe LED chip 92 is increased, and for maintaining the proper lightemission, the heat should be conducted from the longer strip portion 91a to the circuit board. One way to facilitate the heat conduction is tobroaden the strip portion 91 a (hence the lead frame 91) to which theLED chip 92 is attached.

While the width of the longer strip portion 91 a is to be increased, theoverall size of the case 93 may be unchanged so that the light-emittingdevice X is kept compact. In this case, the side walls of the case 93need to be made thinner to permit the size increase of the longer stripportion 91 a. This configuration, however, will weaken the frame-holdingforce of the case 93, which may allow the lead frame 91 to drop off fromthe case 93.

SUMMARY OF THE INVENTION

The present invention has been proposed under above-describedcircumstances, and thus an object of the present invention is to providea semiconductor light-emitting device that is compact and capable ofemitting bright light.

According to the present invention, there is provided a semiconductorlight-emitting device comprising: a lead frame including a bondingregion having a top surface and a bottom surface; a semiconductorlight-emitting element mounted on the top surface of the bonding region;and a case covering part of the lead frame. The bottom surface of thebonding region is exposed to an outside of the case. The lead frameincludes a thin extension extending from the bonding region and having atop surface and a bottom surface. The top surface of the thin extensionis flush with the top surface of the bonding region, while the bottomsurface of the thin extension is offset from the bottom surface of thebonding region toward the top surface of the bonding region.

Preferably, the semiconductor light-emitting device of the presentinvention may further comprise a thick extension extending from thebonding region and having a top surface and a bottom surface. The thickextension is arranged adjacent to the thin extension and is the same inthickness as the bonding region. The bottom surface of the thickextension is exposed to the outside of the case.

Other features and advantages will be apparent from the followingdescription with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating the principal portions of asemiconductor light-emitting device according to the present invention.

FIG. 2 is a bottom view illustrating the semiconductor light-emittingdevice shown in FIG. 1.

FIG. 3 is a sectional view taken along lines III-III in FIG. 1.

FIG. 4 is a sectional view taken along lines IV-IV in FIG. 1.

FIG. 5 is a sectional view taken along lines V-V in FIG. 1.

FIG. 6 is a sectional view illustrating a conventional semiconductorlight-emitting device.

FIG. 7 is a sectional view taken along lines VII-VII in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings.

FIGS. 1-5 illustrate a semiconductor light-emitting device according tothe present invention. The semiconductor light-emitting device Aincludes a lead frame 1, a light-emitting diode (LED) chip 2, a case 3,and a protection resin 4 that allows the passage of light emitted fromthe LED chip 2. The light-emitting device A is a small rectangularparallelepiped having a length of about 4 mm, a width of about 1 mm, anda height of about 0.6 mm. In FIG. 1, for convenience of explanation, theprotection resin 4 is not shown.

The lead frame 1 is made of Cu, Ni, or an alloy containing Cu and/or Ni.As shown in FIG. 2, the lead frame 1 is exposed out of the case 3 at itsbottom surface, and is divided into a longer primary portion and ashorter secondary portion. The primary portion includes a bonding region11, a plurality of thin extensions 12, and a plurality of thickextensions 13. In FIG. 1, the boundary between the bonding region 11 andthe extensions 12, 13 is indicated by double-dot broken lines.

The bonding region 11 is a strip-shaped region on part of which the LEDchip 2 is mounted. Each of the thin extensions 12 extends out from thebonding region 11, and has a thickness which is about half the thicknessof the bonding region 11, for example. As shown in FIG. 4, the topsurfaces of the thin extensions 12 are flush with the top surface of thebonding region 11. The bottom surfaces of the thin extensions 12 arepositioned higher than the bottom surface of the bonding potion 11, asviewed vertically in FIG. 4 (in other words, the bottom surfaces of thethin extensions 12 are offset toward the top surface of the bondingregion 11 from the bottom surface of the bonding region 11). The bottomsurfaces of the thin extensions 12 are covered by the case 3.

As shown in FIG. 5, each of the thick extensions 13 extends out from thebonding region 11, and has a thickness which is substantially the sameas the thickness of the bonding region 11. The top surfaces of the thickextensions 13 are flush with the top surface of the bonding region 11,and the bottom surfaces of the thick extensions 13 (which are flush withthe bottom surface of the bonding region 11) are exposed to the outsideof the case 3. As shown in FIGS. 1 and 2, the thin extensions 12 and thethick extensions 13 are arranged alternatively in the longitudinaldirection of the lead frame 1.

The LED chip 2 as a light source of the light-emitting device A isconfigured to emit light of a predetermined wavelength. The LED chip 2is made of a semiconductor material such as GaN, for example, and emitsblue light, green light, or red light by the recombination of electronsand holes at an active layer sandwiched by an n-type semiconductor layerand a p-type semiconductor layer. The LED chip 2 is connected to theshorter portion of the lead frame 1 via a wire 5.

The case 3 is made of a white resin, for example, and is a generallyrectangular frame. As shown in FIGS. 3-5, the inner surfaces of the case3 serve as a reflector 3 a that tapers downward. The reflector 3 aupwardly reflects light which is emitted laterally from the LED chip 2.As shown in FIG. 4, the case 3 is held in unreleasable engagement withthe thin extensions 12. Further, as shown in FIG. 2, the case 3 is inmesh with the thin extensions 12 and the thick extensions 13.

The protection resin 4 is made of a transparent or transparent epoxyresin, for example, filled in a space defined by the case 3. Theprotection resin 4 covers the LED chip 2, and while protecting the LEDchip 2.

Next, the functions of the semiconductor light device A will bedescribed below.

As described above, the case 3 is held in unreleasable engagement withthe thin extensions 12. Thus, the lead frame 1 is reliably held by thecase 3, to be prevented from dropping off from the case 3. As a result,though the light-emitting device A has a very small width (about 1 mm),the lead frame 1 is exposed out of the case 3 in a relatively largearea, as seen from FIG. 2. Therefore, heat can be efficiently conductedfrom the LED chip 2 to a printed circuit board, for example, whichcontributes to attaining light emission of desired intensity.

As described above, the thin extensions 12 and the thick extensions 13are arranged to alternate with each other, and the bottom surfaces ofthe thick extensions 13 are exposed to the outside of the case 3, asshown in FIG. 2. In this manner, the exposed area of the lead frame 1can be increased. Advantageously, this facilitates the heat dissipationfrom the led chip 2.

1-2. (canceled)
 3. A semiconductor device comprising: a first lead frameincluding an upper surface and a lower surface spaced from each other ina thickness direction; a semiconductor element mounted on the uppersurface of the first lead frame; a second lead frame spaced apart fromthe first lead frame in a first direction, the second lead frameincluding an upper surface and a lower surface; a case covering a partof each of the first lead frame and the second lead frame; and a wireconnecting an upper surface of the semiconductor element and the uppersurface of the second lead frame; wherein the first lead frame includesa first exposed portion provided with an upper surface and a lowersurface that is exposed from the case, the second lead frame includes asecond exposed portion provided with an upper surface and a lowersurface that is exposed from the case, the first lead frame includes afirst thin extension smaller in thickness than the first exposedportion, the first thin extension extending from the first exposedportion in a second direction perpendicular to both the first directionand the thickness direction, the second lead frame includes a secondthin extension smaller in thickness than the second exposed portion, thesecond thin extension extending from the second exposed portion in thesecond direction, the first thin extension includes an upper surface anda lower surface, the upper surface of the first thin extension beingflush with the upper surface of the first exposed portion, the lowersurface of the first thin extension being covered with the case, and thesecond thin extension includes an upper surface and a lower surface, theupper surface of the second thin extension being flush with the uppersurface of the second exposed portion, the lower surface of the secondthin extension being covered with the case.
 4. The semiconductor deviceaccording to claim 3, wherein the first lead frame includes a first endand a second end opposite to the first end, the first end being closerto the second lead frame than the second end is, the first thinextension being disposed at the first end of the first lead frame. 5.The semiconductor device according to claim 3, wherein the second leadframe includes a first end and a second end opposite to the first end ofthe second lead frame, the first end of the second lead frame beingcloser to the first lead frame than the second end of the second leadframe is, the second thin extension being disposed at the first end ofthe second lead frame.
 6. The semiconductor device according to claim 3,wherein the semiconductor element is mounted on the first exposedportion.
 7. The semiconductor device according to claim 3, wherein thesecond exposed portion includes a wire bonding region to which the wireis bonded.
 8. The semiconductor device according to claim 3, wherein thesecond lead frame includes a third thin extension smaller in thicknessthan the second exposed portion, the third thin extension extending fromthe second exposed portion in the first direction.
 9. The semiconductordevice according to claim 8, wherein the second thin extension and thethird thin extension are continuously connected to each other along anedge of the second exposed portion.
 10. The semiconductor deviceaccording to claim 3, wherein the first lead frame includes a fourththin extension smaller in thickness than the first exposed portion anddisposed adjacent to the first thin extension, and the first lead frameis formed with a first recess located between the first thin extensionand the fourth thin extension, the first recess being indented in thesecond direction relative to both the first thin extension and thefourth thin extension.
 11. The semiconductor device according to claim10, wherein the first lead frame includes a thick extension greater inthickness than both the first thin extension and the fourth thinextension and located between the first thin extension and the fourththin extension.
 12. The semiconductor device according to claim 10,wherein the first lead frame includes a fifth thin extension smaller inthickness than the first exposed portion and disposed adjacent to thefourth thin extension, and wherein the first thin extension, the fourththin extension and the fifth thin extension are arranged at sameintervals in the first direction.
 13. The semiconductor device accordingto claim 7, wherein the case covers the second lead frame in a mannersuch that the wire bonding region is exposed from the case.
 14. Thesemiconductor device according to claim 3, wherein the second lead frameincludes a terminal opposite to the first lead frame and is formed witha second recess located between the terminal and the second thinextension, the second recess being indented in the second directionrelative to the second thin extension.
 15. The semiconductor deviceaccording to claim 10, wherein the first thin extension and the fourththin extension are aligned in the first direction.
 16. The semiconductordevice according to claim 3, wherein the case includes a bottom surfaceflush with the lower surface of the first exposed portion.
 17. Thesemiconductor device according to claim 3, wherein the first thinextension includes an end spaced from the first exposed portion in thesecond direction and embedded in the case.
 18. The semiconductor deviceaccording to claim 10, wherein the first lead frame includes a terminalprotruding from the case in the first direction, the first lead frame isformed with an additional recess facing the first recess in the seconddirection, and a distance between the first recess and the additionalrecess is equal to a size of the terminal of the first lead frame in thesecond direction.
 19. The semiconductor device according to claim 3,wherein the lower surface of the first thin extension is parallel to theupper surface of the first exposed portion.
 20. The semiconductor deviceaccording to claim 3, wherein the first lead frame includes an uprightportion connected to both the lower surface of the first exposed portionand the first thin extension, the upright portion being perpendicular tothe upper surface of the first exposed portion.
 21. The semiconductordevice according to claim 10, wherein the first lead frame is elongatedin the first direction, and the first recess corresponds in position tothe semiconductor element in the first direction.